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Topic Review (Newest First)

03-24-2012 08:51 PM

leverhead

Thanks Racer. I'll let you know if I need the shims...they may come in handy. I probably won't have the cam and springs for another 10 days or so. Regards.

03-24-2012 11:39 AM

raceman14

OK, The distance between the cam button and the timing cover needs to be shimmed to .001" or as close as you can get. You can buy small shims, you can even use brass or steel washers the same OD as the hole in your timing chain. As long as the cam button stays in place the shims will never go anywhere.

If you have not checked the vertical dimensions of the timing gear and the crank gear you should. In 35 years of building SBC's I have never found them to be closer than .005". To zero drag and distributor timing scatter you need to get that number as close to .001" as possible once you determine where your cam gear is going to be you have to place shims between the crank and the crank gear. If you can't find them I have them made 100 at a time in small .001" .005" increments. It might be overkill as most timing chains have enough slop in them to compensate for some mis-alignment, if you want you engine to run like a top, it does not take that much longer to do it right and it is not real expensive, just time consuming.

Once you get the little bugs worked out you will see how rock solid your timing gets as the ring gear on the cam can vary timing a couple degrees just on .005" slop.

03-24-2012 09:11 AM

leverhead

Racer,
Good morning. I'm checking the gap between the cam button and timing cover....cam 'walk' if you will.

I had the cam pushed in against the torrington thrust bearing (just a plain brass washer or ring - about .030 thickness) and a roller type cam button in front.

The chain is not pulling it forward. I installed the cover then pulled the cam forward to see how much it walked.

Thanks for asking.

Also to note, my intake valves are 2.08 (124.8 grams vs 116.5 grams for a 2.05) so I'm still trying to factor in spring weight and rev kit spring pressure and wonder if the crane springs (part# 99893 - 150 seated @ 1.8, 340 @ 1.3) will be enough.

03-23-2012 11:49 PM

raceman14

Lever,
When you say endplay where are you measuring?

If the cam is bottomed against the block and you have a shim in there how are you getting end play?

Is the timing chain pulling the cam forward and you push it back .025"?

I ask because I am trying to make sure you don't have additional problems.

03-23-2012 09:10 PM

leverhead

Raceman,
Thanks for the input. Actually the cam is being sent back for a full refund. I'll be going with a custom grind from Crane - i like their billet stock and their cam specs more closely resemble what I need for this motor and my altitude here in NM. Should be a 'normal' grind with cast gear. I'll also be changing out the springs with their recommended springs (150 seated @ 1.8, 340 @ 1.3). I'm also running an Isky rev kit so I can get away with much lower pressure with that also.

The base varied from .903 to .908 when myself and a 3rd party mic'ed it. Yes I have Eagle H beam stroker rods (6") and they are very close but enough clearance with the small BC. Also we mic'ed the lobes and they were inconsistent in height and width all along the length of the cam....and not a split pattern like I ordered. This was a wierd one.

I'll be swapping out the intake rockers for 1.6 with the replacement cam for some added lift as the exhaust is fine but the intake could use some extra.

Yes the endplay will be set when I mock up the new one. The previous one had some serious alignment issues (inconsistent pattern throughout the length of the cam and very close to the inside edge) and that was with a thin .030 brass ring behind the gear and the cam pushed all the way in. It still had approx .025 or more of endplay. I'm expecting the next cam to align with the lifters correctly (and wider lobes) then I can get the gear alignment and endplay correct.

Thanks for the offer. I'll let you know. Regards.

03-23-2012 05:15 PM

raceman14

Lever,
You are going to kill 25hp with those springs and you will kill your engine oil and valvesprings with the heat they generate. If you were turning 9500 you might need that much pressure.

If you don't run stroker rods you can hit the cam in a couple places with standard rods. That looks like about an .850" base circle with the optical mics.
That cam will lose you about 2-3% of your duration at the valve unless it was compensated for in the grind ( usually not done ). You can check it with your degree wheel when you dial it in.

I might be tempted to go up from 1.5 -1.6 on the rocker to get some back.

That cam is similar to the GM ASA cam that I use in my "Outlaw" crates, with stock GM604 parts and the cam swap, those engines at 350" make about 475HP swapping in a 3.75" stroke and stroker pistons that same engine makes about 550HP. I use my "Outlaw" spring set on them and they are good to 7500 and are a German made 1.260" spring with 175# @1.800 and 425 open, I sell them **************

Cam end play is your responsibility not the cam manufacturers. I set mine as close to ZERO as I can get it. First you have to set your crank gear in place, then you put your cam gear in place those two have to be shimmed to vertical +/- .001" once you do that you shim your cam end play to zero with shims behind the cam gear / bearing and the nose bearing against the timing cover. If you can't find the stuff ************

03-21-2012 09:33 PM

leverhead

I mocked up the cam to check endplay and lobe alignment. Endplay with my roller cam button was excessive but worse was the lobe alignment. With the cam pushed back as far as it will go as installed, and a light film of red grease on the rollers, I can see a few of the lifters are directly centered on the lobe but most are off to one side (the inside edge) with many sitting right on the inside edge of the lobe. So any endplay will cause the lifter roller to hang off the edge. Pics attached. I'll give comp a call tomorrow to see about rectifying this.

03-21-2012 05:27 PM

joelster

Quote:

Originally Posted by ap72

with a 230/236 cam? You must have some amazing heads, an awesome EFI system, and a super light car! Any pics of the car? Is it a kit car?

Huh?

My cam is 256/260, EFI, AFR 227's, and race weight of around 3100. No tune either. Should be knocking on 9's either this summer or in the fall. It's a 4th gen f-bod, 94 Z28.

If there is a dimensional problem. Send it back for a QC check... Maybe send some photos first... That's all I was saying...

03-21-2012 06:25 AM

ap72

Quote:

Originally Posted by joelster

Comp is 11.77-1, pump gas, street car, my altitude is around 700 ft.

with a 230/236 cam? You must have some amazing heads, an awesome EFI system, and a super light car! Any pics of the car? Is it a kit car?

03-21-2012 05:37 AM

joelster

Comp is 11.77-1, pump gas, street car, my altitude is around 700 ft.

03-20-2012 08:38 PM

leverhead

I agree I could get away with lighter springs. They were installed by World Castings when the heads were purchased and rated up to .700 lift. (1.550 diam). The cam I removed was a 260 @ 50, .602 lift 108 lsa with rev kit , rockers are summit aluminum rollers (1.5) and the intake valves are 2.08 so they were sufficient. Comp suggested their springs (954-16) for the new cam which are actually heavier (but slightly smaller diameter) so I figure I would use what I already have and save the $$$.....probably more than I need but still in the safe zone. I may rethink the springs though...

Still dont get the narrow lobe thing...

BTW, what compression ratio are you running...and at what altitude? Is this a street car? Thanks.

03-20-2012 07:48 PM

joelster

I would think those springs are overkill for that camshaft you are running. I ran a 242/248 duration with .584"/.579" hydraulic roller with a single beehive spring. It was 130 seat and 313 open (going off the top of my head here). You are running 480lbs with less duration and less lift, probably a lobe rate similar to what I was running. If you are running heavy rockers or heavy valves then they might be necessary but I bet it would be fine with a 918 beehive spring.

My new cam is 256/260 with lift near .700" with heavy Crower maximus roller lifters, shaft rockers, and big pushrods, and my springs are similar to what you have right now.

03-20-2012 07:40 PM

leverhead

The roller face is approx 11/32 and the lobes are about 15/32. The lobes on the cam I took out are 1/16" wider. The roller I checked seem to line up in the center of the lobe with a smidgon leftover on each side, so I assume as long as the endplay is within spec it won't be a problem...just a little close for my taste and dont know why they made them so narrow. Could not get a definitive answer from Comp.

Springs are 200 @ 1.9", 480 @ 1.2" (Motown heads / -3). Comp also recommended their springs if starting from scratch (210 @1.9, 523 @ 1.25) so I figure I'll use what I already have installed, as well as my rev kit - should be plenty without being excessive.

The pic of the bottom cam looks very similar. Comp doesn't tell you the base circle size but my measurements show about .908. I originally was going to go with an LT1 grind but lowered the duration a bit because of my elevation (5500-6000 ft) and compression ratio (9.8:1) . Also went with the small base circle as that was what the other cam was and looking down the cam journals the rods look really close (6" eagle H beam) so I felt safer that way. Thanks for posting those pics....I feel a LITTLE better now.

03-20-2012 06:53 PM

joelster

Here is a nasty .950" base for an LT1/sbc

Here is a really nasty .900" base for an LT1/sbc

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